Ah, I think I see what they're saying. I think that's actually a result of bad coding more than anything else. Here's my theory:
On certain games, the machine has to "spool" information from the DVD as the game is playing. This technique was introduced back on the PS1 for
Soul Reaver, I believe. Where the system only has to "load" the initial starting point.. after that, as you move to a new area, the new information is spooled from the disc, and is waiting in memory before you get there, for seamless gameplay with no load times. It seems logical that an "open" game like GTA would use this feature.
I don't think the problem is in the laser itself, but rather than guidance system that moves the laser around.
If a game is properly coded, then all of the relevant information for the spooling would be located on one section of the disc, so that the laser doesn't have to move that far in order to load everything it needs.
However, if the information it needs is scattered around the disc, then the laser has to do a lot of jumping around in order to load everything. This is what makes that "clicking" noise that some people report. This can also cause stutters in the game and/or audio, if the laser is having a hard time keeping up with the spooling.
Blood Omen 2 suffered horribly from this, constantly stuttering as new sections were loaded, and you could hear the laser scurrying around the disc trying to collect all the data on the new section.
MGS3 also suffers from this.. the "skipping audio" some people complain about in codec conversations. I've heard this stuttering, and I can also hear the laser on my PS2 going from one end of the disc to the other, over and over again during codec conversations. This means that, while the game itself runs just fine, the coding of the game itself isn't "optimized" for spooling, that the system is having to scan over the entire surface of the disc to get what it needs for one small section.
The end result is a motor, gear, or belt that wears out and/or breaks so the laser can no longer move properly. Which, for a spooling game like GTA, would result in a DRE.
Luckily, I don't think GT4 uses the spooling technique. I've never once heard my PS2's laser skipping around once a race is loaded. Most likely, the track and cars are small enough files that the system only has to load them once, and they're then stored in memory, requiring no further spooling from the disc.
It IS possible, specifically in GT4, that unusually large tracks may require spooling (specifically, Nürburgring, and possibly LeMans, if that track is there). Owners of the no-time-limit BMW demo, and possibly owners of the new demo could confirm whether or not the PS2 is spooling the track as it plays that course.
But so long as the game is fairly well laid out on the disc, it shouldn't stress the system any more than normal.
Me, I've got a first-gen PS2.. 30001, launch unit. So if anyone's PS2 is going to die, it'll probably be mine.. hehe. But it's never given me any trouble so far.. I get the occasional DRE's, but never on a game.. always on a CD, DVD, and most especially on DVD-Rs (since my set-top player won't touch a DVD-R). I'm not particularly worried about it, though. It's never given me a DRE on a game, and although it has gotten quite a bit of use lately, I've had stretches where I haven't turned the thing on for months at a time. So even though mine's "older", it probably has a lot fewer hours on it than other launch units. So long as it lasts me until the PS3 comes out, I'm good.
Although if mine does die right after GT4 comes out, you'll hear about it, don't worry.
